Essentially, cable lacing involves running a thin cord (traditionally waxed linen, according to Wikipedia—though standard twine would work for most purposes) along the length of the cables you're running together, looping the cables together at regular intervals. When you need to break a few cords out of the group, just don't include them in the next loop down the line. Cable lacing often uses an overhand knot called a "marline hitch" to secure the cords at each interval; you can see the marline hitch in action here.

Whether or not you actually need to break cords out of the group, cable lacing is a simple alternative to cable sleeves. It's a classic method that's been used in telecommunication, naval, and aerospace applications forever (also according to Wikipedia), but with the surfeit of cords on your desk, you could easily put this cable management method to good use.